On my 66 I have a few electrical issues, thinking they are related..Battery is brand new, alternator was just tested at oreilly showed good putting out over 14amps. With the car running and I put my voltmeter on the battery it’s only showing 12.4 or so running. The battery fully charge is 12.56. So it doesn’t appear I’m getting any charging, when I do the old school test and put my voltmeter on the red hot wire on the alternator and ground the other one it shows at 12.4 or less. I just replace the regulator thinking that might be it? Nothing changed. Now my fuel gauge isn’t working my driver side light on my blinker is not lighting up, while driving my generator light will slowly come on and then slowly go off. And my dash lights don’t seem to be on for the speedometer. Was there some ground strap that is synonymous with all these different issues.? I’ve tested the tank sender, its brand new as well. I had the dash restored, I’m suntanning to be convinced maybe one of those ground straps that are internal in the dash is not hooked up or something. How does the circuitry work on this car from where to where to where? Any help would be appreciated

 

You need to buy an original Chassis Service Manual and a Fisher Body Manual for your car. They are available on Ebay often.

 

I have them, shows a tan wire from tank, shows a green wire for power, power is on the green wire when I pulled the cluster pin. It does not explain well what powers what unless I just am not reading it correctly

 

All sensors including the fuel tank operate the ground side of the circuits. Power is supplied directly to the gauge or idiot light.

 

That does not help me, not trying to sound ungrateful, but The problem is I have a very , or not so very basic understanding of how this cars circuitry works. No insult intended to you. But as you see what I have performed in testing and what I am seeking for information does not fall in line with your comments..best if somebody could have a phone conversation to better help me understand this situation.

 

Generally, you should expect the person who tested your ALT to have done it correctly but what you described in your testing implies a faulty regulator or faulting ALT as you should be getting ~14.3V at the battery car running at idle no accessories running. Quick test with car running turn headlights on, increase and decrease engine RPM. Headlights should remain a constant brightness throughout RPM ranges as a good ALT will maintain correct voltage supply. Bad ALT will often demonstrate fluctuation in headlight brightness as RPM increases and decreases. It might still be wiring maybe, but this quick test often provides some insight. You have a disparity for sure between what the person testing the ALT found and what you’re seeing. ALT is not charging if you’re only reading 12V.

 

I had it tested at Oreilly’s auto parts, I watched him put it on the test machine, type in the code and it-actually gives you a print out showing output, as well I have two alternators in my garage, put both of those on, still shows the same 12.4, 12.2 etc at the battery car running, both those alternators show 12.6 off the power wire of the alternator. My multi meter is good, went to my buddies house, tested his single wire alternator on his nova, showed 14.4.. Its not the alternator for sure, puzzling for sure, then the fact dash lights not coming on, fuel guage pegged full and alternator light lightly glowing intermittently while driving

 

Sounds like a voltage regulator to me. I recently trouble-shot my charging system, that had a "new" VR. The "new" VR was shiny and dust-free. It just didn't work. After various testing proved it didn't work, I replaced it with another "new" VR and problem solved. I also took the time to disconnect and clean (with 240 grit sand paper) all connectors among the battery, alternator, Horn Relay/Power Distribution Terminal, and voltage regulator. Much Better, now. Good Luck!

 

In my post I stated I just put a new voltage regulator on it yesterday, nothing different. Thats why I am perplexed. Its odd that the fuel guage isn’t working, the dash lights not working, only one light of the blinker lights, drivers side blinker light isnt glowing etc. when you turn the key to on, the alternator light,oil light etc in dash doesn’t illuminate yet driving down the road those two lights will intermittently start to glow on and off

 

All too often we've seen a new VR installed w/ no benefit or resolution only to find the new VR is bad - it happens more often than you'd suspect. When you get erratic light flickering I generally always suspect corrosion &/or bad negative (ground) terminal connections. If you have not done it already, remove your battery terminal ground connections and clean them at the chassis/frame & block locations. As suggested, wire brush and sand the terminal ends of the cables themselves and the block/frame/chassis mounting locations. The ground (negative) terminals are most often the culprits. You can't pump juice back into the battery with poor grounding. Contrary to conventional (popular) conceptions, electrons flow (out) from the negative (anode) battery terminal through the vehicle's block/frame/chassis and return into the positive (cathode) battery terminal. Resistance (corrosion/loose nuts/bolts, etc.) encountered in the negative (ground) path make it difficult to find the return (positive) pathway. You need a solid negative (ground) established - it's good/routine maintenance often overlooked but simple.

 

 

Norm, I just transitioned my 66 to a track pack w30, so the brand new battery in trunk, brand new correct diameter positive and negative cables, a ground the frame to clean metal when securing ground cable to the frame in the rear, used the correct fat ground strap up front from engine to frame. So I think I have that covered. When I check my alternator at the positive red wire and ground the volt meter to a bolt it reads 12.4 or so. Dash was restored, wondering if one of the metal dash ground points is causing the other issues and possibly creating this alternator issue? Considering alternator oil light do not illuminate when key is turned to on etc

 

Andy, I believe I am tracking along with you. I will note you did not mention in your discussion (above) your negative battery terminal cable connection to the block of the engine - perhaps an oversight or am I misreading/misinterpreting? Yes, you grounded (appropriately sized cables) from engine to frame & battery to frame. The negative battery terminal needs to go directly to the engine block. Anything attached to the engine (alternator) obtains its ground path off the engine - not the frame i.e. alternator secures its ground from the engine. What I am attempting to suggest is your alternator does not obtain its ground either via the frame or the chassis. It receives its ground directly from the engine. Where is your negative battery terminal connected? It should be connected directly to the block of the engine. You might be considering your ground should be OK by employing a good ground from battery to frame &/or battery to chassis. That is not how/where the alternator achieves its ground and if this is your assumption, think about the circuitous pathway the alternator has to travel to find a dedicated ground. The negative battery terminal needs to go directly to the engine block.

 

Norm,
I certainly do not have the electrical experience to challenge this, however every 66 W30, or correct track pack car is grounded exactly like I did it. Curt Anderson sent me the factory directions on exactly how Oldsmobile instructed this be done, ground cable attaches to frame under the trunk, big fat ground strap from the frame on drivers side to the engine block, goes on the stud where the bottom power steering bracket attaches to the block. What you are saying is I would need to run a car length ground cable to the engine block like I did the positive cable. Curious how W30 cars worked if this is the only way?

 

There is nothing wrong with the grounding cable system on a W30 car. It grounds to the frame in the front and rear,so it has a solid ground provided the grounding pointsd are chean and bare.

 

You want the absolute least resistance from the alternator ground to vehicle ground (battery). You want this least amount of resistance so electrons can flow unimpeded (w/o resistance) from the negative battery terminal to the alternator. This is why the negative terminal of the battery is connected to the engine block - least amount of resistance from alternator to vehicle ground source (battery). If you had a brand new spanking car with a brand new spanking frame (no rust, no stray grounds, etc.) you could employ the method you are choosing. But, here you are "dependent" on there being no stray grounds (either a ground fault interrupt or ANY increased resistance from the rear of the car, through the frame (and most likely chassis, as well) up to the steering bracket where (in your case) the alternator will find its ground source. That's a fair amount of metal which must be traversed along the way to achieve a solid dependable ground pathway from the alternator to the negative terminal of the battery - assuming there are no ground faults and no items increasing the resistance along this pathway. Yes, it can be done - it is not the preferred method. The choice is yours alone. To answer your question directly regarding what I'm saying is to run a car length of cable to the engine block - my answer to you is emphatically - yes. You have an irregular non-charging alternator. The least resistance to a ground pathway is from the ground side of the alternator to the negative (ground side) of the battery terminal - it's quite simple, indeed. I cannot speak to what may possibly be increasing resistance along the pathway you've chosen which might possibly be contributing to a non-charge 12.4V condition - but it isn't charging the battery if that's the case. It "should" work for you yes, but is it? I don't know, are you providing a clear pathway to ground? You aren't providing ~14.3V to the battery with the alternator. I'm offering you a suggestion, what you do with it is your decision. You might hard wire the ground side (case) of the alternator directly to your negative battery terminal and see if the alternator responds accordingly. Good Luck.

 

Fully agree. The caveat, of course, is in assuming there is no resistance to ground along that pathway.

 

I need to re- look at all ground connections, make sure there are no interruptions..( like I believe there is under the dash) . Let me try to sort this all out and report back..Thanks all, Norm appreciate your information on all this as well as Mike’s..Now I know where to start

 

If you connect a separate dedicated ALT ground (case) wire directly to battery negative (-) post (ground) & the ALT begins to work it tells you the issue resides in the ground (negative) path to the battery negative post. It's that simple to test - you're specifically tied dead-on to the negative terminal of the battery. At a minimum if the ALT begins to charge, you've found the issue is on the ground (negative). The issue might still be a faulty VR (new ones are well known to be bad) if the ALT doesn't begin to charge. I'm not suggesting it cannot be on the (+) wiring path, but the fact you have flickering, inconsistent dash lights, GEN light comes on, fades, fuel gauge is pegged, etc. suggests the issue resides on the ground (negative) path & not the positive wiring path. As Eric suggested earlier "All sensors including the fuel tank operate the ground side of the circuits". You can save yourself some time by doing a fast hookup from the ALT to the negative battery terminal to rule out the ALT isn't grounding properly. Good Luck.

 

If the alternator bench tests good but puts out only 12v at the output post on the car, that alternator is suspect.

Do you have the small braided ground straps from engine to firewall and firewall to frame in place? Broken or missing can create a world of hard-to-diagnose electrical problems.

On your dash issues- you say it's been apart and supposedly restored. Look in your 66 CSM wiring diagram and make sure all wires in the printed circuit connector are oriented correctly in the plug, and that the plug is installed correctly in the PC. The plug and dash are supposed to be keyed so the line workers can install them quickly, but 56 years down the road who knows what brittle plastic might have caused.

 

1) Ignition switch 12v source is thru RED 12ga wire from junction block to switch.

2) 9A INST B/U fuse is powered from IGN terminal on ignition switch thru PINK wire.

3) INST B/U fuse powers: backup and parking brake warning lamps, the ALT, OIL and TEMP warning lamps, and the fuel gauge thru a GREEN/WHITE stripe wire in the dash printed circuit connector.

4) Warning lamps and fuel gauge are powered thru a common buss on the printed circuit, fed by the GREEN/WHITE wire. Printed circuit busses are indicated on the wiring diagram by black/white hashmarks.

5) Ground side of the components:
i) fuel gauge grounds thru the TAN wire to the tank sending unit.
ii) oil pressure warning grounds thru BLUE/WHITE stripe wire to the oil sending unit on engine.
iii) temp warning grounds thru GREEN wire to temp switch on engine. Also thru ignition switch for bulb test on starting engine.
iv) alt warning traces back to the voltage regulator and ignition switch thru a BROWN wire.

Get yourself a spray can of electrical contact cleaner along with some brass wire toothbrushes. Don't be afraid to use them on any electrical connection you can get to.